WASHINGTON — The capture of a notorious drug kingpin by Mexico’s armed forces represents a significant victory for the government and highlights the emerging role of the country’s marines in the violent battle against cartels, analysts say.

The successful capture comes as the Mexican marines have developed a close training relationship with their American counterparts.

A contingent of about two dozen U.S. Marines have been in Mexico training their counterparts in small-unit infantry tactics.

The American Marine contingent is made up of personnel on temporary assignment who rotate into the country and are limited to training, said John Cornelio, a spokesman for U.S. Southern Command. “They don’t go outside the wire,” he said.

The focus on the role of Mexican marines comes in the wake of their role in the capture of notorious drug kingpin Miguel Angel Treviño Morales outside the border city of Nuevo Laredo on Monday. Treviño Morales was the leader of the violent Zetas cartel and had long eluded capture.

He was nabbed by Mexican marines who swooped in and intercepted a pickup driving along a road in northern Mexico. He was captured with $2 million and a small arsenal of weapons. The U.S. military was not involved in the ground operation.

The role of the U.S. military in Mexico has long been sensitive because of the specter of imperialism that has historically cast a shadow over relations between the two countries.

But as Mexico’s armed forces have been plunged further into the war on drug cartels, the U.S. military has stepped up help with mobile training teams and exchange programs.

“The relationship between the two militaries just continues to grow,” Cornelio said.

The role of Mexico’s navy and marines is emerging as an important player in the fight against cartels, analysts say. Mexico’s 200,000-strong army is a more traditional force with a strong nationalist strain that runs through its officer corps, said George Grayson, a professor at William & Mary and an expert on Mexico.

The smaller navy and marines have been more open to outside influences, and their troops tend to be better educated and trained, said Roderic Camp, a professor at Claremont McKenna College who has written extensively about Mexico. The Mexican marines have 21,500 troops but are expanding to 26,560, according to the International Institute for Strategic Studies.

The Mexican marines have been quicker than the army to act on intelligence, which is often supplied by the United States, Camp said.

That has boosted the confidence of U.S. agencies that share intelligence with the Mexicans, he said.

“Of all the operational units in Mexico that are directed toward the cartels, they’ve proven to be the most effective,” Camp said of the marines and navy.

“The navy is a modern force,” Grayson said. “The navy is the favorite interlocutor in terms of military to military relations.”